The Government acted unlawfully by approving a strategy to meet the UK’s climate targets, a High Court judge has ruled.

Environmental charities Friends of the Earth and ClientEarth, and the Good Law Project, took joint legal action against the Department for Energy Security and Net Zero over its decision to approve the Carbon Budget Delivery Plan (CBDP) in March 2023.

The plan outlines how the country will achieve targets set out in the sixth carbon budget, which runs until 2037, as part of wider efforts to reach net zero by 2050.

The three groups argued at a hearing in February that the then-secretary of state, Grant Shapps, acted unlawfully by approving the plan as he lacked information on whether individual policies could be delivered in full.

In a ruling on Friday, Mr Justice Sheldon ruled in their favour, stating that Mr Shapps’ decision was “simply not justified by the evidence”.

He said: “If, as I have found, the Secretary of State did make his decision on the assumption that each of the proposals and policies would be delivered in full, then the Secretary of State’s decision was taken on the basis of a mistaken understanding of the true factual position.”

The ruling marks a second High Court victory for the three groups against the Government over its climate policies.

In 2022, a different judge ruled the Government’s Net Zero Strategy was unlawful as ministers were not properly briefed on how individual policies would help meet climate targets set out in the sixth carbon budget, as required by the 2008 Climate Change Act (CCA).

In the CBDP case, the groups claimed that Mr Shapps had no or inaccurate information from different Government departments about the risks related to enacting climate policies under the plan, which gave a “misleading summary” of whether they could be put in place.

David Wolfe KC, representing FoE, told the court that some “risk tables” – used to demonstrate the risks associated with delivering each policy – were “recast” to remove information about whether plans could be implemented.

The tables were not shared with Parliament, climate bodies or the public, meaning the plan could not be properly scrutinised, the court heard.

Lawyers for the Government said that Mr Shapps had “sufficient information” which “rationally supported” his decision.

But in his 50-page ruling, Mr Justice Sheldon said that the minister “could not evaluate for himself” which policies in the CBDP would fail and which would be delivered based on the information provided.

He said the details in the draft plan were “vague and unquantified” and did not provide Mr Shapps with “sufficient” information on whether the plan should be approved.

Speaking following the ruling, Friends of the Earth lawyer, Katie de Kauwe, said: “This is another embarrassing defeat for the Government and its reckless and inadequate climate plans.

“It shows the strength of the Climate Change Act – brought into force after a successful campaign led by Friends of the Earth and the backing of an overwhelming majority of MPs – to hold the Government of the day to account for meeting its legal requirements to cut emissions.

“We urgently need a credible and lawful new action plan that puts our climate goals back on track and ensures we all benefit from a fair transition to a sustainable future. Meeting our domestic and international carbon reduction targets must be a top priority for whichever party wins the next general election.”

Sam Hunter Jones, a senior lawyer for ClientEarth, said: “The courts have now told the UK Government not once, but twice, that its climate strategy is not fit for purpose. This time the court made it emphatically clear: the Government cannot just cross its fingers and hope for high-risk technologies and uncertain policies to plug the huge gaps in its plans.

“No more pie in the sky – this judgment means the Government must now take credible action to address the climate crisis with a plan that can actually be trusted to deliver and with numbers that can be relied on.

“The good news is that with crisis comes opportunity. As its own expert advisers have repeatedly said, the Government has a golden opportunity to reduce emissions with actions that will also create jobs, improve services and bring down household bills.”

Emma Dearnaley, legal director of Good Law Project, said: “This welcome ruling shows that the law is our best, and often last, line of defence against a Government that is failing to act as it must to address the climate emergency. And we will continue to use it to push for accountability and greater ambition”.

In response to the decision, a DESNZ spokesperson said: “The UK can be hugely proud of its record on climate change. Not only are we the first major economy to reach halfway to net zero, we have also set out more detail than any other G20 country on how we will reach our ambitious carbon budgets.

“The claims in this case were largely about process and the judgment contains no criticism of the detailed plans we have in place. We do not believe a court case about process represents the best way of driving progress towards our shared goal of reaching net zero.”

While the CBDP remains government policy, the DESNZ said it will publish a new report within 12 months following the judge’s decision.